4. Monarch Caterpillars

There are four stages in a butterfly’s life-cycle: egg, caterpillar (larva), chrysalis (pupa), butterfly.

Adult monarch butterflies live from one to eight months depending on the season. The monarch caterpillar lives for less than a month.

Toward the end of life females lay 500 slightly oblong period-sized eggs glued to milkweed leaves, one per leaf. Eggs stick to the leaves through wind and rain.

After 3-6 days, caterpillars hatch. Monarch caterpillars are striped in yellow, black, and white from end to end. Over 20 days caterpillars eat 30 milkweed leaves, grow, and molt five times.

Instead of “Eat like a horse” we should say “Eat like a caterpillar.” From hatching out of the egg to forming a chrysalis, caterpillars increase their mass by a factor of at least 2,000!

Click here (2 caterpillars) and here (5 caterpillars) for pictures of caterpillars at different stages of growth.

Poison from the milkweed makes caterpillar and butterfly indigestible to predators. Milkweed is so bitter that it gives the caterpillar and butterfly a dreadful taste. Predators quickly learn to leave them off the menu. After eating monarchs, blue jays have been seen throwing up.

Milkweed has insect defenses including heart toxins and sticky sap that gums up insect mouths. But monarch caterpillars are immune to the toxins. They circumvent the sticky sap by cutting the sap vein near the stem before eating the leaf from the tip.